1. Field of the Invention
The present invention relates to a chain-drive power transmission apparatus, and more particularly to an improved chain tension control apparatus for preventing chain chattering in a chain-drive power transmission system, which is capable of preventing a chain from generating a vibration noise by appropriately maintaining a chain tension thereof.
2. Description of the Background Art
In general, a chain-drive power transmission system employing a pair of sprockets driven by a chain which is engaged thereonto is widely applied to a variety of industrial appliances, such as transportation vehicles.
Conventionally, as shown in FIG. 1, a chain-drive power transmission apparatus includes main and free wheeled subordinate sprockets 1a, 1b, and a chain 2 engaged onto the main and free wheeled subordinate sprockets 1a, 1b for power transmission. Here, reference numeral 3 denotes chain rollers.
The chain 2 is formed by serially engaging a plurality of steel link plates into one another, and it is generally classified into a roller chain and a silent chain.
The silent chain is adopted to obtain a smooth and silent operation but is complicated in structure, so that it is only employed in limited fields due to its high production cost. Consequently, the roller chain is broadly employed.
However, although it is an advantage in that a larger amount of power may be transmitted at a constant rate, the conventional power transmission apparatus using a roller chain tends to generate vibration or noise due to its structural disadvantages.
Such vibration and noise are generated as a result of metal-to-metal friction. In particular, external and internal factors may produce errors in straightness, alignment and pitch with regard to the sprockets 1a, 1b. Further, a long-term operation and subsequent wear of the sprockets 1a, 1b may cause a connection problem between the sprockets 1a, 1b and the chain 2, thereby increasing the noise.
For instance, as shown in FIG. 2, a chain roller 3 during the operation of chain 2 tends to incline towards a side wall "B" rather than towards a bottom center "A" of a U-shaped groove 4 that receives and passes the roller 3, thereby producing a further noise.
Moreover, a main reason for the noise generation in the chain-drive power transmission apparatus is attributable to a decreased tension in the chain 2. That is, when the chain 2 is loosened by the decreased tension therein, an impact between the respective sprockets 1a, 1b and the chain 2 causes a serious chain chattering noise which results from the chain 2 vibration.
Here, a variety of methods are being considered in order to restrain noise generation. As an example, a buffer is supplied in the U-shaped groove 4 in order to decrease the noise that may be caused by friction between the chain rollers 3 and the main and free wheeled subordinate sprockets 1a, 1b. As another example, a chain guide shoe is fixedly provided between the main and free wheeled subordinate sprockets 1a, 1b and the chain 2, for thereby decreasing vibration noise that may be caused by decreased tension of the chain 2.
However, the buffer installation in the U-shaped grooves 4 of the main and free wheeled subordinate sprockets 1a, 1b is complicated, and easily generates an abrasion thereof. Also, the chain guide shoe installation leads to an impact noise between the chain guide shoe and the chain 2.